updated resource details cover img and usage #3 (#8348)

### WHY are these changes introduced?

Fixes #8330 and #8336

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### WHAT is this pull request doing?

Updated 2 images on the resource details page to remove blur according
to updated visual style and [remove rich text
editor](#7944 (comment))
to reduce confusion, as that is not a Polaris component

Author: Raquel Breternitz